The antimicrobial compounds are widely used in bacterial remedies in various industrial processes, drinking water, waste management, daily use cosmetics, and furniture. These have applications in water treatment, personal care products, paints and coatings, wood preservation, food and beverages preservations. These are widely used to control the growth of pathogenic microorganisms or to eliminate them from inanimate objects, surfaces or intact skin.
One of the most widespread uses of antimicrobials is in personal care formulations, antidandruff shampoos wherein they are formulated (as actives/preservatives) in both leave-on and rinse-off preparations. They are also used as biocides in anti-fouling paints, which is a specialized coating applied to the hull of a ship or boat to slow the growth of organisms that attach to the hull and can affect a vessel's performance and durability.
Commonly used antimicrobial compounds are quaternary ammonium compounds, biguanides, alcohols, aldehydes, ethylene oxide, anionic agents, organic acids, metallic salts, isothiazolinones, peroxides, chlorine compounds and halogens. These compounds are sometimes included in liquid coating compositions that are applied to a substrate and that become dry films. It is desirable that such dry films control surface fungi and algae and also present as little adverse effect as possible on health and the environment.
In antifouling paints the most commonly used biocides are Irgarol 1051, diuron, Sea-nine 211, dichlofluanid, chlorothalonil, zinc pyrithione, (2,3,3,6-tetrachloro-4-methylsulfonyl) pyridine (TCMS), 2-(thiocyanomethylthio)benzothiazole (TCMTB) and zineb. All these agents have different mechanism of action and have different preferred end use. Since the partial ban on the application of organotin biocides, especially tributyltin (TBT) in antifouling paints for small marine vessels, these new generation of surrogate antifouling biocides have been increasingly used. These surrogate biocides are often applied in conjunction with copper (Cu) compounds such as cuprous oxide, copper thyocyanate or metallic copper to control Cu-resistant fouling organisms. Of these, zinc pyrithione has been widely used as an antifungal and antibacterial agent.
Zinc pyrithione as an antimicrobial compound is used around the world in a variety of applications including antifouling paints, building products, plastics, polyurethane products, textiles and antidandruff shampoos. Zinc pyrithione is approved for over-the-counter topical use in the United States as a treatment for dandruff. It is the active ingredient in several anti-dandruff shampoos. It is also used as a preservative in personal care products, in building products, plastics and polyurethane products, as well as biocide in textiles.
Although zinc pyrithione is known as an excellent antimicrobial component with broad range of activity against wide variety of microorganisms, there is a continuous demand for an effort to develop advanced zinc pyrithione containing antimicrobial compositions of high antimicrobial efficacy with the reduced blending amount of zinc pyrithione and multiple add-on benefits as per the end use. When used in personal care applications, it is desirable that the formulation should have improved scalp and/or hair conditions and reduced inflammation. Similarly, when used in paints and coatings, it is desirable that there should be low leaching rate of biocide, prevention and/or inhibition of in-can discolouration of composition and low environmental toxicity for various paint and coating applications. It is also desirable that the final product should be effective even at lower concentration of the active.
The prior art is replete with various references which disclose various methods to increase the efficacy of pyrithione salt by using them either in various combinations or formulating them appropriately so that their delivery at the required site increases.
US Publication No. 2004/0058855 describes a method of delivering excess zinc to eukaryotic cells (fungi, yeast) through zinc ionophoric material along with a zinc containing material to inhibit the cell metabolism. The invention also relates to a method of treating microbial infections on the skin or scalp by delivering excess zinc and thus provide improved anti-fungal/anti-dandruff activity.
U.S. Pat. No. 5,939,203 discloses discoloration prevention in pyrithione-containing coating compositions by using zinc oxide along with zinc pyrithione. U.S. Pat. Nos. 6,908,912 and 7,455,851 disclose a stable, soluble, antimicrobial composition where insoluble metal salts of pyrithione in combination with a zinc source (zinc salts, -oxides, -hydroxides, -borates, -sulfates, -chlorides etc.) were solubilised in alkanolamines. These reported compositions deliver higher concentration of pyrithione and zinc ions to an application (in-can preservatives and metalworking fluids) and thus provide enhanced biocidal efficacy against microorganisms and bio-films. U.S. Pat. No. 7,026,308 describes a topical scalp care composition with enhanced anti-dandruff efficacy containing zinc pyrithione, a metal ion source and strong chelating agent.
However, the antimicrobial compositions disclosed in these patents readily form insoluble precipitates as the concentrations of pyrithione and the zinc source are increased to develop a concentrated biocidal composition. These insoluble precipitates reduce the effectiveness of the composition as an antimicrobial agent and do not provide aesthetic benefits to the products.
U.S. Pat. No. 8,501,725 discloses a synergistic combination of flumetsulam or diclosulam with zinc pyrithione. U.S. Pat. No. 8,691,726 discloses synergistic combination of a glyphosate compound and zinc pyrithione. These combinations have greater activity than would be observed for the individual antimicrobial compounds.
U.S. Pat. No. 8,119,168 describes personal care compositions containing zinc oxide and zinc pyrithione, a detersive surfactant, sodium bicarbonate and water. The pH of the composition is greater than 7 and the zinc oxide has a relative zinc lability of greater than 15%.
Khattar and Salt in Journal of Antimicrobial Chemotherapy, 1993, 175-177 reported the enhancement in anti-bacterial activity of pyrithione against Klebsiella pnenmoniae bacteria specifically in combination with zinc chloride.
Although zinc pyrithione is known as an excellent antimicrobial component with broad range of activity against wide variety of microorganisms, but there is a continuous demand for an effort to develop additional combinations of antimicrobial compounds with relatively low impact on health and/or the environment. Accordingly, what is needed in the art is antimicrobial composition that is highly efficacious against variety of microorganisms and bio-films at reduced active concentration, does not have environmental and toxicological effects and can provide multiple benefits for various personal care, paint, coating, industrial applications like improved scalp and/or hair conditions, reduced inflammation, low leaching rate of biocide and prevention or inhibition of in-can discolouration of composition.
The present invention provides novel composition of zinc pyrithione with zinc salt especially zinc salt of pyridine carboxylic acid salt. The combination produces synergistic effect as compared to zinc pyrithione when used alone or pyridine carboxylic acid salts alone. The combination also shows reduced leaching of the biocide from paint composition. The present invention also provides various personal care, paint, coating and industrial compositions comprising such synergistic composition. These compositions have enhanced efficacy and have widespread scope in end use.